1. Field of the Invention
The present invention relates to an image forming apparatus for forming an image on a recording material such as a sheet according to an image forming command given from outside the apparatus and transporting the sheets to a sheet post processing means upon executing post processing. The present invention also relates to a sheet discharging device of the image forming apparatus and method of controlling the sheet discharging device.
2. Description of the Related Art
An image forming apparatus forms an image on a sheet in accordance with an image forming command (signals indicating the printing request contents) from an external apparatus such as a host computer, and then discharges the sheet to a standard discharging port of the image forming apparatus. Conventionally, when handling a large number of sheets, there have been proposed various kinds of methods in which a sheet discharging device having a recording material postprocessing means for carrying out the postprocessing of the recording material, e.g., sorting the sheets, staple processing, etc., is connected to the discharge side of the image forming apparatus to be controlled (see Japanese Patent Application Laid-open No. 2002-268502, for example).
However, the sheet discharging device of the above-described structure has the following issues.
The sheet discharging device is provided with a staple unit for performing staple processing, and the staple unit is provided with a staple cartridge for housing staples and a staple detecting sensor for detecting the existence of the staples. Upon detecting that there are no staples within the staple cartridge, the sheet discharging device informs a controller that there are no staples, and displays on an operation panel that the staple cartridge needs to be exchanged. In that case, the user exchanges the staple cartridge, and instructs the image forming apparatus to perform initial setting of the staple cartridge through an operation panel. For example, the initial setting can be an operation which lets out a head of the staple. The operation means operation that exposes the staple tips.
Upon receiving the instruction of the initial setting, the image forming apparatus feeds a recording material to be used for the initial setting, and performs idle striking on the recording material transported to the staple unit of the sheet discharging device to bring out the staple within the staple cartridge to the stapling position. In this way, it has not been conventionally possible to exchange the staple cartridge and perform the initial setting, without an instruction from a user and without needing a recording material for idle striking to perform the staple preparation processing.